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Demineralized (HCl/HF) samples of Beypazari lignite were oxidized in air at 150 °C for up to 120 h in a ventilated oven. Elemental analyses, diffuse reflectance Fourier transform infrared (DRIFT), solid-state 13 C CP/MAS/TOSS NMR, and pyrolysis mass (Py-MS) spectroscopies as well as solvent swelling were used for the characterization of the oxidized and unoxidized samples. It was found that the removal of 90.1 % of the mineral matter from Beypazari lignite facilitated the access of oxygen into the coal structure and permitted the occurrence of diffusion-controlled reactions. This was confirmed by the observation of linear relationships between the decrease in the intensity of aliphatic CH 2 and CH 3 groups, the increase of the O/H atomic ratio and the decrease in the aliphatic factor, and the square root of the duration of oxidation

The detection by fast atom bombardment mass spectrometry (f.a.b.-m.s.) of high molecular mass (greater than 1000 Da) material in coal-derived products was investigated. The pentane insoluble (PI) fractions of liquefaction extracts from maceral concentrates of two UK coals (Linby and Cortonwood), prepared in a low-residence time (less than 10 s) flowing-solvent reactor and fractions of hydropyrolysis tar prepared in a hot-rod reactor at 500 °C were examined.F.a.b.-m.s. spectra of the Cortonwood liptinite concentrate liquefaction extract PI-fraction mounted in a thiodiethanol matrix indicated ions up to molecular masses of about 4000 Da. This appears to be the highest reported molecular mass identified by fast atom bombardment in a coal-derived material. Other liquefaction extract PI-fractions showed somewhat lower molecular masses. The phenolic, basic nitrogen and aromatic fractions of the hydropyrolysis tar indicated ionization up to molecular mass limits between 1500 and 2000 Da. Comparison of these results with size exclusion chromatography (s.e.c.) showed agreement with results for the hydropyrolysis tar fractions; however, the presence of molecular masses in excess of 10000 Da was indicated by s.e.c. for the liquefaction extract PI-fractions. Not all problems associated with vaporization, ionization and detection of high molecular mass materials in f.a.b.-m.s. appear to have been solved, with the choice (polarity) and preparation of matrices for sample mounting remaining an empirical procedure.

The oxidation of Beypazari lignite was carried out in air at 150°C for up to 168 h. Oxidized samples were withdrawn from a ventilated oven at different periods of time and chacterized by elemental analysis, diffuse reflectance Fourier transform infrared (DRIFT), solid-state 13 C CP/ MAS/TOSS NMR, and pyrolysis mass (Py-MS) spectroscopies. It was found that oxidation influence the organic structure and the inorganics at different periods of the oxidation. Iron(II) sulfate was formed in 24 h, during which time there was almost no change of aliphatic CH 2 and CH 3 groups

Product distributions from the atmospheric pressure pyrolysis of sugar-cane bagasse and silver birch were determined in a wire-mesh reactor as a function of temperature (300–900 °C) and heating rate (1–1000 K s−1), over a range of holding times between 0 and 100 s. Major groups of components present in the tars were identified by g.c.-m.s.. Above 500 °C when increasing the heating rate from 1 to 1000 K s−1 in experiments using holding times longer than several seconds, tar yields were observed to increase by about 10 wt% to nearly 54% w/w daf bagasse; total volatile yields increased by similar amounts. Number average molecular masses (MMn) of tars determined by vapour pressure osmometry (v.p.o.) were in the range 150–250 Da, those of silver birch tars being systematically larger than those of sugar-cane bagasse by 15–30 Da. For both sets of tars, MMn were observed to decrease with increasing temperature between 400 °C and 600 °C, but remained unchanged between 600 °C and 900 °C. The molecular masses were also observed to decline with increasing heating rate. Lignocellulosic substrates appear to cleave readily to give relatively small, compact and relatively stable molecules able to evaporate completely at temperatures around 500 °C. Extensive chemical modification of primary products appears to result from intraparticle secondary reactions, these reactions being intensified during pyrolysis at higher heating rates. Whilst the wire-mesh reactor configuration appears not to alter tar yields or structures subsequent to release from parent substrate particles, comparison with tars obtained at 600 °C in a ‘hot-rod’ (fixed-bed) reactor suggests that whilst overall yields may be adversely affected and the relative abundance of some major components altered, extraparticle secondary reactions do not substantially change the character of the tar at this temperature.

A flowing-solvent (F-S) liquefaction reactor with a continuous solvent sweep through a fixed bed of coal has been developed. In contrast to liquefaction experiments using closed (batch) reactors, where products remain within the reactor for the duration of the experiment, solubilized liquefaction products are continuously swept out of the reaction zone. In this way the possibility of retrogressive reactions is minimized. Results are presented and compared with data obtained in a mini-bomb (M-B) reactor under comparable conditions and using the same sample of Point of Ayr coal. Conversion data indicate that, unlike M-B experiments performed under similar conditions, no increase in solid residue is observed during long residence time-high temperature runs in the F-S reactor. Size-exclusion chromatography shows that products from the F-S reactor increase in molecular weight with increasing reaction time and temperature whereas, due to secondary reactions, products from the M-B reactor are generally observed to decrease in molecular weight as the severity of the reaction conditions is increased.

Publisher Summary This chapter discusses the pyrolysis of maceral concentrates effect of heating rate and pressure on product yields and structures. The development of pyrolysis reactors capable of operating over wide ranges of heating rates have enabled the measurement of variations in product distribution because of changes in sample timetemperature history, in isolation from changes in other experimental parameters. Atmospheric pressure and high-pressure wire-mesh pyrolysis reactors are equipped with gas sweeping through the sample holder and are designed to operate over wide ranges of heating rates. The relatively high Point of Ayr durain yields compared to the corresponding clarain also appear related to the greater liptinite content of the durain. With increasing hydrogen pressure, the whole-coal (composed of 60% inertinites) and the inertinite concentrate shows parallel monotonically increasing total volatile yields.

Publisher Summary This chapter presents the comparison of pyrolysis tars and liquefaction extracts obtained under conditions minimizing secondary reactions. It presents a study in which samples prepared from a set of UK softening bituminous coals were pyrolyzed in a wire-mesh reactor where the sample holder was swept with a stream of gas to remove volatiles away from the reaction zone and the apparatus was designed to operate over a wide range of heating rates and hold times at the target temperature. The pentane insoluble (PI) fraction of the liquefaction extracts was isolated by concentrating the product mixture in a rotary vacuum evaporator followed by precipitation in chilled pentane. The molecular mass distributions from both sets of PI fractions show greater amounts of large molecular mass material than the corresponding pyrolysis tars, suggesting occurrence of molecular size reduction prior to tar release from coal particles. Average molecular masses of PI fractions appear to change but little with increasing reaction temperature, and with conversion, for both the vitrinite and liptinite concentrates. The liptinite concentrate-derived samples appeared to have larger molecular masses than the corresponding vitrinite-concentrate-derived samples.

A lignite (67.2% C daf) and a coal (89.0% C daf) have been reductively ethylated by Sternberg's procedure 4 and the spectra, in particular the 1 H and 13 C n.m.r. spectra, of the products have been obtained. The distribution of hydrogen atoms and, in less detail, of carbon atoms in the reductively ethylated fuels has been determined. It is emphasized that both reductively ethylated fuels contained a variety of structures. The carbon aromaticities of the reductively ethylated lignite and the reductively ethylated coal were 0.41 ± 0.08 and 0.40 − 0.54 respectively. The aromatic nuclei of the reductively ethylated coal were more highly substituted than those of the reductively ethylated lignite. The 1 H n.m.r. spectra indicate that the reductively ethylated coal and lignite possessed ≈3.5 and ≈2.5 substituents per benzene ring respectively. Resolved absorption in the 13 C n.m.r. spectra suggests lower figures than these and it was evident that some of the benzene rings in both materials but especially in the reductively ethylated lignite were lightly substituted. The 13 C n.m.r. spectra show that both materials contained branched and unbranched paraffin chains. Much of the 13 C n.m.r. spectra however consisted of unresolved absorptions and the 13 C n.m.r. measurements suggest that the reductively ethylated materials consisted of rigid, relatively immobile molecules of moderate molecular weight. 13 C n.m.r. absorption by carbon atoms adjacent to aromatic rings was amongst that which was not resolved — though the rings themselves gave resolved absorptions — and this suggests that the aromatic rings were on the periphery of a rigid, perhaps alicyclic, structure.

Manvers coal was pyrolysed to 500 °C in an atmosphere of deuterium using an autoclave described previously1. The final pressure was 2.64 MPa. Deuterium-hydrogen ratios were found to be 0.4 in the resulting semicokes (by diffuse reflectance infrared spectrometry), 1–2 in selected tar compounds (by g.c.-m.s.), 1.1 in the liquor (from refractive indices) and 0.16 in the hydrocarbon gases (by high-resolution m.s.). These ratios were unaffected by the addition to the coal of 5% of either tetralin or pyrite. The relative proportions of deuterated methanes, dibenzofurans and C3 phenols were consistent with the random scrambling of deuterium and hydrogen atoms. The distributions of other deuterated hydrocarbon gases and tar compounds showed deviations from the predictions of random scrambling. The ineffectiveness of deuterium in capping radicals is emphasised and the results are explained in terms of the inhibition of the diffusion of deuterium and hydrogen by the development of plasticity during pyrolysis.

The infrared spectra of four samples of soft brown coal of Miocene age which varied systematically both in colour and in attrinite:densinite ratio have been determined. The spectra of the coals were very similar to each other as were those of the coals which had been benzoylated or acetylated and this suggests that the chemical structures of attrinite and densinite must be similar and that little difference exists between the lithotypes. © 1981. North Atlantic Treaty Organization The remission measurements,t he maceral analyses, the proximate and ultimate analyses recorded in Table 1 were carried out by Erik Thomsen (Aarhus, Denmark) to whom the authors are sincerely grateful. The work forms part of an investigation of the geochemistry of lignite directed by Professor Dr G. Ataman and supported by NATO funds for international scientific cooperation.

Samples of a coal and a lignite were boiled in pyridine, partially reduced and partially deuterated by modified Birch reductions. These samples were slowly pyrolysed in an inert atmosphere in a horizontal tube furnace to temperatures in the range 300–600 °C. The yields and the nature of the products are reported; in particular an attempt is made to characterize the various tars, and the pyrolyses are described in terms of a simplified mechanism. It was found that boiling the fuels in pyridine increased the subsequent yield of tar and increased the proportion of high-boiling material within the tar. Tar formation was diffusion-controlled. The role of hydrogen atoms from the hydroaromatic structure of the fuels in the formation of tar, liquor and gas was confirmed. Experiments with partially deuterated fuels established that during pyrolysis interchange of hydrogen atoms occurred amongst the molecules of the gas. Further pyrolyses of partially deuterated coals under wider conditions should be profitable.

A reductively ethylated lignite and a reductively ethylated coking coal have been oxidized by alkaline nitrobenzene. The products of the oxidation were separated into fractions by extraction with organic solvents, and the compounds present in the resulting solutions were characterized by a combination of gas chromatography and mass spectrometry. These compounds had molecular weights less than 300 and the oxidation, though mild, had fragmented the reductively ethylated fuels. Many problems remain, but the method appears to lead to an understanding of the structures of reductively ethylated solid fuels. The structures of the oxidation products are listed and discussed; in general they confirm the interpretation of the n.m.r. spectra of reductively ethylated solid fuels 2 .

A detailed comparison is made between the chemistry and structure of an oil shale and that of lignite. It is suggested that oil shales give phenols on pyrolysis only when they have been derived from vegetation containing lignins.

The infra-red spectra of Tertiary lignites are related to their chemical structure and geology. Pleistocene (62–67% C) lignites and woody peat gave similar spectra to lignins especially in having peaks at 1500, 1450 and 1410cm −1 , Pliocene-Palaeocene (66–74% C) lignites showed no peak at 1500cm −1 and broad absorption throughout the region 1450-1400cm −1 , whilst coals show marked absorption in this region only at 1450cm −1 . These observations are consistent with Manskaya's finding of 35–70% lignins in young lignite. Attention is drawn to the fact that lignites show no infra-red absorption by aromatic CH stretching vibrations. Chars prepared by pyrolysis of lignites did show absorption by aromatic CH stretching vibrations, confirming that dehydrogenation of the lignites took place during pyrolysis. Infra-red spectra of some chemically treated lignites have been recorded.

Three Tertiary lignites have been oxidized with nitrobenzene and sodium hydroxide at 200 °C in a sealed tube. A scheme of extraction has been used to separate the oxidation products and the resulting solutions have been characterized by their infra-red and ultraviolet absorption spectra and by spot tests. The products contain phenolic hydroxyl and carbonyl — rather than carboxyl — groups. Some of the solutions have been reduced and their n.m.r. spectra recorded. The oxidation procedure shows promise as a method of determining the structure of lignites.

Two low-rank mature coals have been oxidized with alkaline nitrobenzene. Soluble phenolic aldehydes and ketones were obtained, similar to those formed from lignites and separable by the same scheme of extraction.

Organic compounds, in particular anthracene and naphthalene, and two coals have been reductively ethylated in tetrahydrofuran (THF) and diglyme using alkali metals to form anions and ethyl iodide to produce ethylates. Product distributions were sensitive to experimental conditions. The rate of anion formation was controlled by their rate of desorption, probably as contact ion pairs, from the alkali metal surface. The enthalpy of formation of a solvated contact ion pair was ?500 kJ mole-1 mainly due to dipole-solvent interaction. 18-crown-6 ether was used to diagnose that, when treated with potassium in THF, anthracepe gave solvated contact ion pairs and probably di-anions whose reactions were characterized by the formation of ethyldihydroanthracene. Naphthalene under identical conditions gave loosely solvated mono-anions which reacted by electron transfer to give diethyldihydronaphthalene. With other alkali metals anthracene and naphthalene gave similar product distributions. The behaviour of other polynuclear aromatic hydrocarbons and of two coals was classified in the same way. It is suggested that when coals are readily solubilized by reductive alkylation mono-alkyldihydro products will predominate. © 1984. Connecticut State Emergency Response Commission A~KNOWLED~E~E~S The authorsa reg ratefult o N. Owen for hisc onstanth elp. 0. Erbaturh asr eceivedg enerouss upportf rom theB ritish Council and the OverseasD eveIopmentA dministration. The work formsp art of a project,‘ The Chemistryo f Solid Fuels’ supportedb y the SERC.

Pyridine extracts of a coking coal and of two lignites have been further separated and the 1H and 13C n.m.r. spectra of the various fractions have been recorded. Three methods of separation were investigated: gel-permeation chromatography, successive extraction with petroleum ether and with benzene as used by previous workers for supercritical-gas extracts, and the classical extraction of the fractions. Gel-permeation chromatography gave most promise of effective separation but the fractions obtained often contained too little material to give n.m.r. spectra. The n.m.r. spectra of the chloroform-soluble material from the pyridine extracts of the coking coal were consistent with a material consisting of polynuclear aromatic nuclei joined through simple bridge structures and possibly also through direct carbon-carbon linkages. The nuclei were substituted by branched and unbranched paraffin chains, some of which were 7 or 8 carbon atoms long. It is probable that alicyclic structures were also present. The aromatic nuclei were mobile in solution. 60% of the carbon atoms were aromatic, and it can therefore be calculated that the molecular weight per aromatic nucleus was 200-300. It is suggested that 13C n.m.r. spectra may be used to characterize chemicals likely to confer coking properties on solid fuels. © 1979. We are grateful to Dr P. Wybel of the Varian Laboratories for arrangingt he field-desorptiona nd field-ionization mass spectrometry. The work has been generouslys upported by the Turkish Scientific and Technological Research Council (TBTAK).